1. Field of the Invention
The present disclosure relates to electrical systems, and more particularly to generators for aircraft electrical systems.
2. Description of Related Art
Electrical systems such as those carried by aircraft commonly employ three stage wound field synchronous generators. The first stage is typically a permanent magnet generator, which is used to supply excitation to the exciter. The second stage is the exciter, which is used to brushless excite the main machine rotor. The third stage is the main machine, which is used to generate power according to excitation applied by the exciter and provide power to the electrical system. The permanent magnet generator, exciter, and main machine are typically operably connected to a common shaft for common rotation with one another.
During operation the output voltage of the main machine can be held constant up to a certain current level, typically up to about twice the rated output of the generator, and thereafter droop rapidly in a short-circuit fault condition. Control of the generator is typically provided by a generator control unit, which is powered by the permanent magnet generator and arranged to control power communicated to the exciter to maintain an output voltage target as output current varies according to the electrical load carried by the generator.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved generator arrangements. The present disclosure provides a solution for this need.